It's easy to be oblivious when you are always looking for the wrong things in people. Elektra scans for distress or danger. She doesn't see anything that doesn't relate to survival in some way. That is what makes this reaction easier for her to understand. It's weakness. Her back straightens when she sees it in preparation to intervene against an enemy that won't show up here.

It's the reminder that no one is coming that makes her change mental tracks. The only one here to trouble Frank is Frank. She scowls to herself as she rises to her feet. It'd be easier if someone were trying to kill him. She very rarely gets this part right, comforting others, but she has to try for Frank.

She pads silently over, resting a hand on his arm in the barest of touches. She can't be sure what's welcome and what isn't. "Something is troubling you." It's stating the obvious without any demand. He doesn't have to tell her anything....

You could tell me, goes unsaid.